diff --git a/src/wf_core/models/input_bindings.py b/src/wf_core/models/input_bindings.py
index 8fee178c..744b5fbe 100644
--- a/src/wf_core/models/input_bindings.py
+++ b/src/wf_core/models/input_bindings.py
@@ -205,6 +205,15 @@ def validate_input_expression_limits(
     visit_expression(value, depth=1, location="expression")
 
 
+def _check_expression_limits(value: object) -> object:
+    """Share the budget validator across graph and schedule bindings."""
+    raw_value = (
+        value.model_dump(mode="python") if isinstance(value, BaseModel) else value
+    )
+    validate_input_expression_limits(raw_value)
+    return value
+
+
 class InputExpressionBinding(BaseModel):
     """Assign one recursively composed expression to a node-local target."""
 
@@ -216,11 +225,7 @@ class InputExpressionBinding(BaseModel):
     @field_validator("expression", mode="before")
     @classmethod
     def check_limits(cls, value: object) -> object:
-        raw_value = (
-            value.model_dump(mode="python") if isinstance(value, BaseModel) else value
-        )
-        validate_input_expression_limits(raw_value)
-        return value
+        return _check_expression_limits(value)
 
 
 InputBinding = Annotated[
@@ -262,11 +267,7 @@ class ScheduleInputBinding(BaseModel):
     @field_validator("expression", mode="before")
     @classmethod
     def check_limits(cls, value: object) -> object:
-        raw_value = (
-            value.model_dump(mode="python") if isinstance(value, BaseModel) else value
-        )
-        validate_input_expression_limits(raw_value)
-        return value
+        return _check_expression_limits(value)
 
 
 for _model in (
diff --git a/src/wf_core/runtime/input_bindings.py b/src/wf_core/runtime/input_bindings.py
index 02c46c2d..f55b200b 100644
--- a/src/wf_core/runtime/input_bindings.py
+++ b/src/wf_core/runtime/input_bindings.py
@@ -3,7 +3,6 @@ from __future__ import annotations
 from collections.abc import Mapping, Sequence
 from typing import Any
 
-from wf_core.conditions import safe_resolve_path
 from wf_core.errors import WorkflowExecutionError
 from wf_core.local_paths import LocalPathError, set_local_value
 from wf_core.models.input_bindings import (
@@ -14,7 +13,11 @@ from wf_core.models.input_bindings import (
     StepInputBinding,
 )
 from wf_core.models.json_values import JsonValue
-from wf_core.runtime.input_sources import SourceResolver
+from wf_core.runtime.input_sources import (
+    GraphSourceResolver,
+    SourceResolver,
+    resolve_composed_expression,
+)
 
 
 def resolve_input_expression(
@@ -27,11 +30,6 @@ def resolve_input_expression(
     location: str,
 ) -> JsonValue:
     """Resolve one composite expression while preserving its payload location."""
-    from wf_core.runtime.input_sources import (
-        GraphSourceResolver,
-        resolve_composed_expression,
-    )
-
     resolver = GraphSourceResolver(
         state=state, workflow_input=workflow_input, context=context
     )
@@ -48,13 +46,44 @@ def resolve_input_expression_with_resolver(
     location: str,
 ) -> JsonValue:
     """Resolve one expression through an explicit typed source resolver."""
-    from wf_core.runtime.input_sources import resolve_composed_expression
-
     return resolve_composed_expression(
         expression, resolver=resolver, label=label, location=location
     )
 
 
+def resolve_step_input_bindings_with_resolver(
+    bindings: Sequence[StepInputBinding],
+    *,
+    resolver: SourceResolver,
+    label: str,
+) -> dict[str, Any]:
+    """Build one node-local payload through an explicit graph resolver."""
+    payload: dict[str, Any] = {}
+    for binding in bindings:
+        location = str(binding.target)
+        if isinstance(binding, InputValueBinding):
+            value = binding.value
+        elif isinstance(binding, InputPathBinding):
+            try:
+                value = resolver.resolve_path(binding.path)
+            except (ValueError, WorkflowExecutionError) as exc:
+                raise WorkflowExecutionError(f"{label} {location}: {exc}") from exc
+        elif isinstance(binding, InputExpressionBinding):
+            value = resolve_input_expression_with_resolver(
+                binding.expression,
+                resolver=resolver,
+                label=label,
+                location=location,
+            )
+        else:
+            raise WorkflowExecutionError(f"unsupported input binding for {label}")
+        try:
+            set_local_value(payload, binding.target, value)
+        except LocalPathError as exc:
+            raise WorkflowExecutionError(f"{label} {location}: {exc}") from exc
+    return payload
+
+
 def resolve_step_input_bindings(
     bindings: Sequence[StepInputBinding],
     *,
@@ -64,35 +93,9 @@ def resolve_step_input_bindings(
     label: str,
 ) -> dict[str, Any]:
     """Build one node-local payload from simple or composite input bindings."""
-
-    payload: dict[str, Any] = {}
-    for binding in bindings:
-        location = str(binding.target)
-        if isinstance(binding, InputValueBinding):
-            value = binding.value
-        elif isinstance(binding, InputPathBinding):
-            try:
-                value = safe_resolve_path(
-                    str(binding.path),
-                    state=state,
-                    workflow_input=workflow_input,
-                    context=context,
-                )
-            except (ValueError, WorkflowExecutionError) as exc:
-                raise WorkflowExecutionError(f"{label} {location}: {exc}") from exc
-        elif isinstance(binding, InputExpressionBinding):
-            value = resolve_input_expression(
-                binding.expression,
-                state=state,
-                workflow_input=workflow_input,
-                context=context,
-                label=label,
-                location=location,
-            )
-        else:
-            raise WorkflowExecutionError(f"unsupported input binding for {label}")
-        try:
-            set_local_value(payload, binding.target, value)
-        except LocalPathError as exc:
-            raise WorkflowExecutionError(f"{label} {location}: {exc}") from exc
-    return payload
+    resolver = GraphSourceResolver(
+        state=state, workflow_input=workflow_input, context=context
+    )
+    return resolve_step_input_bindings_with_resolver(
+        bindings, resolver=resolver, label=label
+    )
diff --git a/src/wf_core/runtime/input_sources.py b/src/wf_core/runtime/input_sources.py
index e2ed1f9b..cdde45cf 100644
--- a/src/wf_core/runtime/input_sources.py
+++ b/src/wf_core/runtime/input_sources.py
@@ -1,11 +1,17 @@
 """Typed source-resolver seam for composed input expressions.
 
-Graph and schedule paths share one composition traversal (literal / array /
-object recursion plus budget enforcement) but keep distinct source models:
-graph leaves resolve ``input`` / ``state`` / ``context`` paths, while
-schedule leaves resolve typed occurrence fields. Do not extend
+Graph and schedule paths share one composition traversal (``_resolve_any``:
+literal/array/object recursion plus budget enforcement via
+``validate_input_expression_limits`` at model validation) but keep distinct
+source models: graph leaves resolve ``input`` / ``state`` / ``context``
+paths, while schedule leaves resolve typed occurrence fields. Do not extend
 ``GraphSourcePath`` with schedule-only roots and do not smuggle occurrence
 values through a faked graph ``context`` mapping.
+
+``wf_api.input_expressions.validate_and_project_input_expression`` keeps its
+own schema-aware recursion (it carries target fragments/locations, not
+runtime values); budget parity there comes from the same model-level
+``check_limits`` validator, not from reusing this value traversal.
 """
 
 from __future__ import annotations
@@ -81,37 +87,62 @@ class MappingSourceResolver:
         return self._values[field]
 
 
-def resolve_composed_expression(
-    expression: InputExpression,
+def _resolve_any(
+    expression: InputExpression | ScheduleExpression,
     *,
-    resolver: SourceResolver,
+    graph_resolver: SourceResolver | None,
+    occurrence_resolver: MappingSourceResolver | None,
     label: str,
     location: str,
 ) -> JsonValue:
-    """Resolve one composite expression through a typed source resolver."""
+    """Resolve one leaf or branch through the shared composition traversal.
+
+    Literal/array/object recursion lives here once for both graph and
+    schedule expressions (same module, same budget validator, same location
+    scheme). Graph leaves need ``graph_resolver``; schedule leaves need
+    ``occurrence_resolver``. Distinct static types keep schedule-only
+    occurrence references out of graph contracts.
+    """
     if isinstance(expression, LiteralExpression):
         return expression.value
     if isinstance(expression, PathExpression):
+        if graph_resolver is None:
+            raise WorkflowExecutionError(
+                f"{label} {location}: graph paths are invalid in schedule bindings"
+            )
         try:
-            value = resolver.resolve_path(expression.path)
+            value = graph_resolver.resolve_path(expression.path)
             return validate_strict_json_value(value)
         except (ValueError, WorkflowExecutionError) as exc:
             raise WorkflowExecutionError(f"{label} {location}: {exc}") from exc
-    if isinstance(expression, ArrayExpression):
+    if isinstance(expression, OccurrenceExpression):
+        if occurrence_resolver is None:
+            raise WorkflowExecutionError(
+                f"{label} {location}: occurrence references are invalid in graph bindings"
+            )
+        try:
+            return validate_strict_json_value(
+                occurrence_resolver.resolve_field(expression.field)
+            )
+        except (ValueError, WorkflowExecutionError) as exc:
+            raise WorkflowExecutionError(f"{label} {location}: {exc}") from exc
+    if isinstance(expression, (ArrayExpression, ScheduleArrayExpression)):
         return [
-            resolve_composed_expression(
+            _resolve_any(
                 item,
-                resolver=resolver,
+                graph_resolver=graph_resolver,
+                occurrence_resolver=occurrence_resolver,
                 label=label,
                 location=f"{location}[{index}]",
             )
             for index, item in enumerate(expression.items)
         ]
-    if isinstance(expression, ObjectExpression):
+    if isinstance(expression, (ObjectExpression, ScheduleObjectExpression)):
         return {
-            field: resolve_composed_expression(
+            field: _resolve_any(
                 value,
-                resolver=resolver,
+                graph_resolver=graph_resolver,
+                occurrence_resolver=occurrence_resolver,
                 label=label,
                 location=f"{location}.{field}",
             )
@@ -120,71 +151,73 @@ def resolve_composed_expression(
     raise WorkflowExecutionError(f"unsupported input expression for {label} {location}")
 
 
+def resolve_composed_expression(
+    expression: InputExpression,
+    *,
+    resolver: SourceResolver,
+    label: str,
+    location: str,
+) -> JsonValue:
+    """Resolve one composite expression through a typed source resolver."""
+    return _resolve_any(
+        expression,
+        graph_resolver=resolver,
+        occurrence_resolver=None,
+        label=label,
+        location=location,
+    )
+
+
 def resolve_schedule_expression(
     expression: ScheduleExpression,
     *,
-    occurrence: Mapping[str, Any],
+    occurrence: Mapping[str, Any] | MappingSourceResolver,
     label: str,
     location: str,
 ) -> JsonValue:
     """Resolve one schedule-side expression against the occurrence environment.
 
-    Composition (literal/array/object) is shared with the graph traversal
-    above; leaves are typed occurrence fields only. Graph paths are invalid
-    here and never reach ``GraphSourcePath``.
+    Accepts a raw occurrence mapping or a ``MappingSourceResolver``; a raw
+    mapping is wrapped so schedule composition reuses the same traversal
+    without faking a graph ``context``. Graph paths are invalid here and
+    never reach ``GraphSourcePath``.
     """
-    if isinstance(expression, LiteralExpression):
-        return expression.value
-    if isinstance(expression, OccurrenceExpression):
-        try:
-            if expression.field not in occurrence:
-                raise WorkflowExecutionError(
-                    f"unknown occurrence field {expression.field!r}"
-                )
-            return validate_strict_json_value(occurrence[expression.field])
-        except (ValueError, WorkflowExecutionError) as exc:
-            raise WorkflowExecutionError(f"{label} {location}: {exc}") from exc
-    if isinstance(expression, ScheduleArrayExpression):
-        return [
-            resolve_schedule_expression(
-                item,
-                occurrence=occurrence,
-                label=label,
-                location=f"{location}[{index}]",
-            )
-            for index, item in enumerate(expression.items)
-        ]
-    if isinstance(expression, ScheduleObjectExpression):
-        return {
-            field: resolve_schedule_expression(
-                value,
-                occurrence=occurrence,
-                label=label,
-                location=f"{location}.{field}",
-            )
-            for field, value in expression.fields.items()
-        }
-    raise WorkflowExecutionError(
-        f"unsupported schedule expression for {label} {location}"
+    resolver = (
+        occurrence
+        if isinstance(occurrence, MappingSourceResolver)
+        else MappingSourceResolver(occurrence)
+    )
+    return _resolve_any(
+        expression,
+        graph_resolver=None,
+        occurrence_resolver=resolver,
+        label=label,
+        location=location,
     )
 
 
 def resolve_schedule_input_bindings(
     bindings: Sequence[ScheduleInputBinding],
     *,
-    occurrence: Mapping[str, Any],
+    occurrence: Mapping[str, Any] | MappingSourceResolver,
     label: str,
 ) -> dict[str, Any]:
     """Build one workflow-input object from schedule-side bindings."""
+    resolver = (
+        occurrence
+        if isinstance(occurrence, MappingSourceResolver)
+        else MappingSourceResolver(occurrence)
+    )
     targets = [str(binding.target) for binding in bindings]
     if has_overlapping_paths(targets):
         raise WorkflowExecutionError(f"{label}: schedule targets overlap: {targets!r}")
     payload: dict[str, Any] = {}
     for binding in bindings:
         location = str(binding.target)
-        value = resolve_schedule_expression(
+        value = _resolve_any(
             binding.expression,
-            occurrence=occurrence,
+            graph_resolver=None,
+            occurrence_resolver=resolver,
             label=label,
             location=location,
         )
diff --git a/src/wf_core/runtime/ops/interrupts.py b/src/wf_core/runtime/ops/interrupts.py
index 8a9c017a..19d39869 100644
--- a/src/wf_core/runtime/ops/interrupts.py
+++ b/src/wf_core/runtime/ops/interrupts.py
@@ -13,7 +13,8 @@ from wf_core.run_state import (
     RunState,
     StepExecutionResult,
 )
-from wf_core.runtime.input_bindings import resolve_step_input_bindings
+from wf_core.runtime.input_bindings import resolve_step_input_bindings_with_resolver
+from wf_core.runtime.input_sources import GraphSourceResolver
 from wf_core.runtime.lineage import commit_foreach_aware_patch
 from wf_core.runtime.ops.flow import advance_frame, append_step_result_trace
 from wf_core.runtime.ops.index import WorkflowIndex
@@ -34,11 +35,11 @@ def build_interrupt_request(
     public_node_id: str | None = None,
     route: InterruptRoute | None = None,
 ) -> InterruptRequest:
-    payload = resolve_step_input_bindings(
+    payload = resolve_step_input_bindings_with_resolver(
         node.request,
-        state=state,
-        workflow_input=workflow_input,
-        context=context,
+        resolver=GraphSourceResolver(
+            state=state, workflow_input=workflow_input, context=context
+        ),
         label=f"interrupt {node.id!r} request",
     )
     validate_payload_against_schema(
diff --git a/src/wf_core/runtime/ops/nodes.py b/src/wf_core/runtime/ops/nodes.py
index 9e02d7e4..da5f5601 100644
--- a/src/wf_core/runtime/ops/nodes.py
+++ b/src/wf_core/runtime/ops/nodes.py
@@ -15,7 +15,8 @@ from wf_core.run_state import (
     RuntimeContext,
     StepExecutionResult,
 )
-from wf_core.runtime.input_bindings import resolve_step_input_bindings
+from wf_core.runtime.input_bindings import resolve_step_input_bindings_with_resolver
+from wf_core.runtime.input_sources import GraphSourceResolver
 from wf_core.runtime.lineage import (
     commit_foreach_aware_patch,
     scope_input_for_frame,
@@ -57,11 +58,14 @@ def _resolve_node_execution(
     context_view = frame_context_view(run, frame)
     context_values = context_view.graph
     state_view = state_view_for_frame(run, frame)
-    resolved_input = resolve_step_input_bindings(
-        node.input,
+    resolver = GraphSourceResolver(
         state=state_view,
         workflow_input=scope_input_for_frame(run, frame),
         context=context_values,
+    )
+    resolved_input = resolve_step_input_bindings_with_resolver(
+        node.input,
+        resolver=resolver,
         label=f"node {node.id!r} input",
     )
     validate_payload_against_schema(
diff --git a/src/wf_core/runtime/subgraphs.py b/src/wf_core/runtime/subgraphs.py
index 42c5bcff..f80f7330 100644
--- a/src/wf_core/runtime/subgraphs.py
+++ b/src/wf_core/runtime/subgraphs.py
@@ -16,7 +16,8 @@ from wf_core.run_state import (
     RuntimeScope,
     StepExecutionResult,
 )
-from wf_core.runtime.input_bindings import resolve_step_input_bindings
+from wf_core.runtime.input_bindings import resolve_step_input_bindings_with_resolver
+from wf_core.runtime.input_sources import GraphSourceResolver
 from wf_core.runtime.lineage import commit_foreach_aware_patch
 from wf_core.runtime.ops.frames import frame_context_view
 from wf_core.runtime.ops.merges import ReducerDefinition
@@ -136,11 +137,13 @@ def _start_subgraph(
 ) -> None:
     prepared.workflow.validate_structure().raise_for_errors()
     parent_scope = run.scopes[frame.scope_id]
-    child_input = resolve_step_input_bindings(
+    child_input = resolve_step_input_bindings_with_resolver(
         step.input,
-        state=state_view_for_frame(run, frame),
-        workflow_input=parent_scope.workflow_input,
-        context=frame_context_view(run, frame).graph,
+        resolver=GraphSourceResolver(
+            state=state_view_for_frame(run, frame),
+            workflow_input=parent_scope.workflow_input,
+            context=frame_context_view(run, frame).graph,
+        ),
         label=f"subgraph {step.id!r}",
     )
     validate_payload_against_schema(
diff --git a/src/wf_core/validation/steps.py b/src/wf_core/validation/steps.py
index f568ba88..a76003ea 100644
--- a/src/wf_core/validation/steps.py
+++ b/src/wf_core/validation/steps.py
@@ -33,6 +33,7 @@ from wf_core.paths import (
     is_valid_destination_path,
     is_valid_source_path,
 )
+from wf_core.runtime.input_sources import walk_expression_paths
 from wf_core.validation.issues import ValidationIssueCode, ValidationReport
 
 
@@ -245,11 +246,9 @@ def _validate_expression_sources(
 ) -> None:
     """Validate every graph path leaf while keeping one top-level target atomic.
 
-    Leaf traversal order is shared with
+    Leaf traversal order is the canonical order defined by
     :func:`wf_core.runtime.input_sources.walk_expression_paths`.
     """
-    from wf_core.runtime.input_sources import walk_expression_paths
-
     for path, suffix in walk_expression_paths(expression):
         _validate_source_path(
             path,
diff --git a/tests/scheduling/test_schedule_expressions.py b/tests/scheduling/test_schedule_expressions.py
index ce404f3e..81800298 100644
--- a/tests/scheduling/test_schedule_expressions.py
+++ b/tests/scheduling/test_schedule_expressions.py
@@ -111,6 +111,53 @@ def test_graph_only_path_is_invalid_in_schedule_bindings() -> None:
         )
 
 
+def test_nested_graph_path_is_invalid_in_schedule_bindings() -> None:
+    with pytest.raises(ValidationError):
+        ScheduleInputBinding.model_validate(
+            {
+                "target": "x",
+                "expression": {
+                    "kind": "object",
+                    "fields": {
+                        "nested": {"kind": "path", "path": "input.a"},
+                    },
+                },
+            }
+        )
+    with pytest.raises(ValidationError):
+        ScheduleInputBinding.model_validate(
+            {
+                "target": "x",
+                "expression": {
+                    "kind": "array",
+                    "items": [{"kind": "path", "path": "state.b"}],
+                },
+            }
+        )
+
+
+def test_nested_occurrence_is_invalid_in_graph_bindings() -> None:
+    from wf_core.models.input_bindings import (
+        ArrayExpression,
+        ObjectExpression,
+    )
+
+    with pytest.raises(ValidationError):
+        ArrayExpression.model_validate(
+            {
+                "kind": "array",
+                "items": [{"kind": "occurrence", "field": "scheduled_at"}],
+            }
+        )
+    with pytest.raises(ValidationError):
+        ObjectExpression.model_validate(
+            {
+                "kind": "object",
+                "fields": {"when": {"kind": "occurrence", "field": "scheduled_at"}},
+            }
+        )
+
+
 def test_invalid_field_rejected() -> None:
     with pytest.raises(ValidationError):
         ScheduleInputBinding.model_validate(
@@ -153,7 +200,7 @@ def test_invalid_resolved_input_fails_schema_check() -> None:
     resolved = resolve_schedule_input_bindings(
         [binding], occurrence=OCC, label="schedule s"
     )
-    with pytest.raises(Exception, match="count"):
+    with pytest.raises(WorkflowExecutionError, match="count"):
         validate_payload_against_schema(
             {"type": "object", "properties": {"count": {"type": "integer"}}},
             resolved,
@@ -161,10 +208,27 @@ def test_invalid_resolved_input_fails_schema_check() -> None:
         )
 
 
-def test_direct_schedule_expression_resolution_rejects_graph_paths() -> None:
+def test_direct_schedule_expression_resolves_literal() -> None:
     expr = ScheduleInputBinding.model_validate(
         {"target": "x", "expression": {"kind": "literal", "value": 1}}
     ).expression
     assert (
         resolve_schedule_expression(expr, occurrence=OCC, label="s", location="x") == 1
     )
+
+
+def test_graph_path_leaf_rejected_inside_schedule_traversal() -> None:
+    from wf_core.models.input_bindings import PathExpression
+
+    from wf_core.runtime.input_sources import MappingSourceResolver
+
+    graph_leaf = PathExpression.model_validate(
+        {"kind": "path", "path": "input.a"}
+    )
+    with pytest.raises(WorkflowExecutionError, match="graph paths are invalid"):
+        resolve_schedule_expression(
+            graph_leaf,  # type: ignore[arg-type]
+            occurrence=MappingSourceResolver(OCC),
+            label="s",
+            location="x",
+        )